The invention relates to an improved odometer of the type generally used on vehicles to record mileage.
Tampering with odometers to reduce the display of mileage has long been a widespread practice in order to defraud both buyers and sellers of cars. Sellers of cars, particularly new cars, each year are cheated by reducing the mileage so that the warranty appears valid. Buyers of used cars are cheated out of hundreds of millions of dollars in buying cars which in fact have much greater mileage than the odometer shows. This latter practice in fact represents a considerable safety hazard, since the purchaser may wrongly assume that vital equipment of the automobile is in good condition, whereas in fact he would know from the correct mileage that the equipment is worn out and perhaps dangerous.
Most of the odometers in use today have a plurality of plastic digit wheels mounted for rotation about a shaft. Each digit wheel is connected to adjacent wheels by gears mounted on intervening carrier plates. Each of the wheels has a plurality of teeth extending around its periphery on one side and engaging one surface of the gear and at least a single tooth on the other side, likewise engaging a gear on the other side, so that for each complete rotation of one digit wheel, the next highest digit wheel is rotated a predetermined distance so as to display the next digit. A gear on one end of the shaft drives the lowest distance wheel to rotate all of the wheels in turn.
Even an amateur can readily reset such a conventional odometer in a few seconds. One simple technique is simply to slip a sharp object between the highest distance wheel and the next highest distance wheel to pry apart the gear and the teeth of the highest digit wheel. The wheel can then be freely rotated to any desired position. In this way, tens of thousands of miles can be removed from the odometer in a few seconds. Alternately, the odometer can be quickly removed from its assembly and the gear plates rotated to any desired position. Yet another technique is to rotate the odometer backward to reduce the displayed mileage. Alternatively, the odometer can be disassembled, the wheels set to any desired mileage and then reassembled.
A number of approaches have been suggested in the past to prevent tampering with odometers, or at least to make tampering as difficult as possible. One technique which has been used is to place a transparent sleeve over the wheel while it is in place so that a sharp instrument cannot be inserted between the digit wheels. The difficulty with this approach is that it does not prevent tampering with the odometer after it has been removed from the automobile, and such removal is normally an easy task. Another technique, as described in Hachtel U.S. Pat. No. 3,495,773, uses a strap which engages the outwardly extending prongs of the carrier plates and prevents rotation of those plates. This technique likewise does not prevent prying or tampering with the odometer after removal.
Another technique is to prevent rotation of the odometer in a backward direction; for example, a linkage between the driving gear and the first wheel can be used which permits rotation of the first wheel only in one direction. This technique alone is not effective since it does not prevent picking of the wheel or disassembly for manual rotation or rotating carrier plates.
One other idea which has found some acceptance involves placing an ink pad on the ten thousand mile wheel so that each digit on that wheel is marked with ink as it rotates. If the wheel is turned back, it is then readily apparent. The difficulty with this approach is that the ink pad dries out during long use of the automobile. Further, the ink can be easily removed from the wheel. There is nothing to prevent substitution of the marked wheel following disassembly of the device.
Yet another approach which has been suggested is to require a sixth wheel, registering in effect millions if kilometers or miles. Such wheel, of course, would prevent an honest mistake where the mileage exceeded one hundred thousand miles. The sixth wheel does not prevent ready tampering of the odometer since it can be turned back as easily as the ten thousand mile wheel.
My previous U.S. Pat. No. 3,785,551, describes a tamper-proof odometer which is an improvement of the above-described techniques. According to that patent, the shaft which mounts the digit wheels is made non-circular to prevent rotation of the gear wheels. Sleeves are affixed to the end of the shaft to make disassembly of the odometer difficult.
The present invention relates to a further improved odometer which makes tampering virtually impossible.
According to the present invention, one of the digit wheels, preferably the ten thousand mile digit wheel, is formed so that if an attempt is made to pry that digit wheel away from the adjacent wheel or to force the internal gears by application of a tangential force to the wheel, and thus reset the wheel, it will break. This provides a readily visible indication to any buyer of the car that an attempt has been made to reset the odometer. The wheel can be made of a brittle material which cannot withstand the application of a force to pry apart the adjacent wheels. Alternatively, the plastic wheel or wheels can be formed with weakened portions such as radially extending grooves to provide scoring so that the wheel will break along the grooves.
In order to prevent disassembly of the odometer, the shaft which mounts the wheels is preferably non-axially grooved, preferably transverse to the axial direction. End caps are preferably attached to the shaft by welding or some other permanent technique. If an attempt is made to cut the end cap or to drill through the shaft along the axial direction, the shaft will break, making reassembly of the unit impossible. Preferably, the end caps have different cross-sectional shapes, for example, rectangular and triangular so that when placed in the mounting structure, they can be oriented in only one direction, that is, the odometer cannot be rotated 90.degree. or 180.degree. to change the displayed mileage.
Of course, the odometer still can be altered by removal from the vehicle and rotating the lowest digit wheel automatically or by hand. Both of these are time consuming and difficult jobs which might well result in the breaking of the shaft in any instance. Of course, the odometer can be broken and replacement parts used to reassemble the unit. Reassembling an odometer is a difficult job in any instance and parts for odometers are not readily available. Accordingly, the present invention makes tampering by an amateur virtually impossible and tampering by a professional unattractive because of the time required and the necessity for additional parts.
Other objects and purposes of the invention will be clear from the following detailed description of the drawings.